Silicon or silica substrate with a modified surface, process for producing the same, new orthoesters and process for producing the same

ABSTRACT

The silicon or silica substrates described have a modified surface of a new type occupied by the alcohol fraction of an orthoester. The alcohol fraction may be saturated or unsaturated. The surface of the substrate is modified by being treated with an orthoester, the water being eliminated from the surface by hydrolysis and then replaced by the resulting alcohol or silylether. Besides many other compounds, new orthoesters having the formula R 1  C OCH 2  --CH 2  --O--CO--CH═CH 2  ! 3 , in which R 1  stands for hydrogen or for a clearable organic residue, R stands for (CH 2 ) n , in which n stands for an integer between 1 and 18, and new orthoesters having the formula (I), are particularly appropriate. In the formula (I), R 1  stands for hydrogen or an organic residue, R 3  stands for hydrogen or an alkyl group with 1 to 6 carbon atoms; and R 4  stands for hydrogen, an alkyl group or an alkyl group or a phenyl group. The modified surfaces have a larger wetting or contact angle, and thus a reduced wettability. In addition, they are capable of reacting with other monomers or polymers by means of all sorts of reactive substituents. This kind of surface modification advantageously replaces the silanization which was up to now usual for glass and other silicates.

This application is a 371 of PCT/CH93/00173 filed Jul. 6, 1993.

The invention refers to a silicon or silicon dioxide substrate with amodified surface and to processes for producing the same, as well as tonew orthoesters and methods for preparing the same.

The modification of surfaces of silicon and silicon dioxide substratesin particular in connection with the development of adhesives oradhesion promotors for such substrates, particularly for glass, so farwas generally based on the idea that the silicon and silicon dioxidesurfaces, respectively, are covered by silanol groups and water. Thus,so far, in the majority of cases such compounds as chloro silanes oralkoxy silanes were used for modifying silicon and silicon dioxidesurfaces, respectively, inasmuch that it was thought that they do reactwith the silanol groups and do form covalent bonds therewith.Accordingly, this method was called "silanization".

Now, the basis of the present invention is the finding that the hydroxylgroups present on the surface of such a substrate, e.g. on a glasssurface, at least partially form part of water which is molecularlybonded to the silicon dioxide surface.

Thus, it is the object of the present invention to provide silicon andsilicon dioxide substrates, which are modified in a novel manner withorganic compounds, have novel properties, and are particularly useful asa basis for anchoring of organic polymers.

Now, said novel silicon and silicon dioxide substrates, having amodified surface, are characterized in that their surface is occupied byan alcohol or a silylether.

Such a modified surface shows an essentially increased boundary orcontact angle for water, as compared with corresponding non-modifiedsurfaces. Thus, the wettability for water is reduced, whereas thewettability for many organic compounds is increased.

In the method for preparing such modified substrates according to thepresent invention the surfaces to be modified are treated with anorthoester.

As is generally known, the term "orthoester" stands for the aliphaticand aromatic esters of the corresponding orthocarbonic acids, which arenot known to exist in free form, thus compounds of the type R¹ --C OR²!₃.

According to the actual status of knowledge it is assumed that, ontreating the surface of silicon or silicon dioxide substrate, an alcoholis formed from the orthoester. Thereby, the water is eliminated byhydrolysis from said surface, and the alcohol or silylether formedthereafter take the place of the eliminated water.

Schematically this may be represented as follows: ##STR1##

Examples of the manifold field of applications of the new technology aresummarized in Table 1 hereafter.

Among the applications listed there, the method according to the presentinvention is particularly useful for modifying the surfaces of glass,quartz, silicon or silicon covered with silicon dioxide. Preferredapplications are e.g. the modification of pyrogenic silicic acid, glasspanes, wafers and oxidized wafers.

By such a treatment, e.g., the adherence of many plastics on thesubstrate can be essentially improved in an inexpensive manner. Inparticular, it allows to directly polymerize onto the substrateadhesives and coating materials, and polymeric interlayers for a laterchemical reaction with adhesives and coating materials.

                  TABLE 1                                                         ______________________________________                                        Product group/products                                                                       Applications                                                                              Utilities                                          ______________________________________                                        1   Silicate fillers                                                          11  Pyrogenic silicic acid                                                                       Hydrophobizing                                                                            Adhesives                                                         Surface coating                                                                           Sealants                                                                      Plastics                                                                      Coatings                                                                      Lacquers                                                                      Colors                                                                        Molding compounds                              12  Precipitated silicic                                                                         Hydrophobizing                                                                            Adhesives                                          acid           Surface coating                                                                           Sealants                                                                      Plastics                                                                      Coatings                                                                      Lacquers                                                                      Colors                                                                        Molding compounds                              13  Silica gels    Hydrophobizing                                                                            Catalysts                                                         Surface coating                                                                           Siccatives                                                                    chromatographic                                                               substrates                                     14  Quartz powder  Hydrophobizing                                                                            Adhesives                                                         Surface coating                                                                           Sealants                                                                      Plastics                                                                      Coatings                                                                      Lacquers                                                                      Colors                                                                        Molding compounds                              15  Glass powder   Hydrophobizing                                                                            Dental products                                                   Surface coating                                                                           Molding compounds                                                             Composites                                     16  Various silicates                                                                            Hydrophobizing                                                                            Zeolites                                                          Surface coating                                            2   Fibers and textiles                                                       21  Glass fibers   Hydrophobizing                                                                            Composites                                                        Finishing   Glass fiber rein-                                                 Adhesion promo-                                                                           forced plastics                                                   tion        Telecomunication                                                              Measuring technique                            22  Glass textiles Hydrophobizing                                                                            Electro laminates                                                 Finishing   Composites                                                        Adhesion promo-                                                                           Glass fiber rein-                                                 tion        forced plastics                                                               Industrial protec-                                                            tion clothing                                  23  Glass wool/rock wool                                                                         Hydrophobizing                                                                            Insulating                                                                    materials                                                                     Building materials                             3   Flat glasses                                                              31  Window glass compo-                                                                          Hydrophobizing                                                                            Insulating glass                                   sites (including                                                                             Adhesion promo-                                                                           windows                                            insulating glass                                                                             tion        Security glass                                     systems)       Surface coating                                                                           composites                                                        Corrosion pro-                                                                            Motor car glass                                                   tection                                                    32  Optical glasses                                                                              Hydrophobizing                                                                            Optical measuring                                                 Adhesion promo-                                                                           technique                                                         tion        Screens                                                           Surface coating                                                                           Photography                                                       Corrosion pro-                                                                tection                                                    33  Glass membranes                                                                              Hydrophobizing                                                                            Chemical measuring                                                Adhesion promo-                                                                           technique                                                         tion        Surface coating                                                   Corrosion pro-                                                                            Biotechnology                                                     tion        Chemical Engineer-                                                            ing                                            4   Special Silicates                                                         41  Silicon wafers for                                                                           Hydrophobizing                                                 electronic and solar                                                                         Surface coating                                                technique      Corrosion pro-                                                                tection                                                    42  Aerogel glasses                                                                              Hydrophobizing                                                                            Technical insula-                                                 Surface coating                                                                           ting layers                                                       Corrosion pro-                                                                            Light glass for                                                   tection     vehicles                                       ______________________________________                                    

"Aerogels" are newly developed materials of the silicate research,having the form of transparent, glass-like bodies, e.g. plates, and aspecific gravity of 0.05 to 0.1 g/cm³. So far, they were notindustrially used, which is thought to be due to their poor resistanceagainst hydrolysis. This drawback can be avoided by treating them withorthoesters according to the present invention.

Silanes cannot be used for hydrophobicity coating wafers, since fromtheir preparation they always contain traces of chlorine. However,chlorine is a strong poison for wafers. Contrary to this, thepreparation of orthoesters can be effected by methods which do not usechlorine.

The modification of surfaces of silicon and silicon dioxide substratesaccording to the present invention shows a number of advantages, ascompared with the use of silanes, i.e.:

The preparation of orthoesters is considerably less expensive than thepreparation of silanes, since it rests on an organic raw material basis,i.e. on petroleum, and thus in general is energetically much morefavorable than the preparation of organic silicon compounds.

They can be prepared by simpler methods, without the use of chlorinechemistry, i.e. in a way which is safer and less harmful to theenvironment.

At least for simple orthoesters, their use is physiologically safe.

Results which are clearer and analytically more easily assertainable areobtained, particularly for coatings.

There is a wide variety of methods for preparing orthoesters which aretailor-made for their specific use thus providing the possibility ofpreparing new or more suitable coatings.

Since, with respect to hydrolysis, the C--O bond is generally morestable than the Si--O bond, more resistent bonding coats over theorganic alcohol adducts late obained as well.

The alcohol moiety of said orthoesters can comprise a hydrocarbonmoiety, the sequence of which may be interrupted by hetro atoms, inparticular oxygen. Also, an aromatic alcohol moiety may be substituted.In particular, the alcohol moiety may be epoxidized, i.e. it may derivefrom glycidyl alcohols.

Prefered are alcohol moieties which either are unsaturated orepoxidized. Thereby, substrate sufaces are obtained which may be furtherreacted by radicalic polymerization or polyaddition with othercompounds.

The following orthoesters of the general formula

    R.sup.1 --C OR.sup.2 !.sub.3

proved to be particularly suitable for the purposes of the presentinvention:

    ______________________________________                                        1.    Trimethyl orthoformate                                                        = orthoformic acid methylester                                                = trimethoxymethane                                                     R.sup.1 = H    R.sup.2 = CH.sub.3                                             2.    Trimethyl orthoacetate                                                        = orthoacetic acid ethylester                                                 = trimethoxyethane                                                      R.sup.1 = CH.sub.3                                                                           R.sup.2 = CH.sub.3                                             3.    Triethyl orthoformate                                                         = orthoformic acid ethylester                                                 = triethoxymethane                                                      R.sup.1 = H    R.sup.2 = CH.sub.2 --CH.sub.3                                  4.    Triethyl orthoacetate                                                         = orthoacetic acid ethylester                                                 = triethoxyethane                                                       R.sup.1 = CH.sub.3                                                                           R.sup.2 = CH.sub.2 --CH.sub.3                                  5.    Tributyl orthoformate                                                         = orthoformic acid butylester                                                 = tributoxymethane                                                      R.sup.1 = H    R.sup.2 = CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.3            6.    Triethyl orthovalerate                                                        = orthovaleric acid ethylester                                                = triethoxypentane                                                      R.sup.1 =  CH.sub.2 !.sub.3 --CH.sub.2                                                       R.sup.2 = CH.sub.2 --CH.sub.3                                  7.    Triallyl orthoformate                                                         = orthoformic acid allylester                                                 = triallyloxymethane                                                    R.sup.1 = H    R.sup.2 = CH.sub.2 --CH--CH.sub.2                              8     Tri(ethylacrylate) orthoformate                                               = orthoformic acid(ethylacrylate)ester                                        = tri(ethoxyacrylate)methane                                            R.sup.1 = H    R.sup.2 = CH.sub.2 --CH.sub.2 --O--CO--CH--CH.sub.2            ______________________________________                                    

The lastmentioned compound 8 belongs to a first group of neworthoesters, i.e. orthoesters of the gneral formula

    R.sup.1 C OR.sup.2 --O--CO--CH═CH.sub.2 !.sub.3        ( 1),

wherein R¹ is hydrogen or an organic residue, and R² is (CH₂)_(n), nbeing an integer from 1 to 18.

The new orthoesters of formula (1) are prepared according to the presentinvention by reacting an acid amide of the general formula

    R.sup.1 --CO--NH.sub.2                                     ( 2)

with benzamide and the corresponding (2-hydroxyalkyl)-acrylate.Preferably, the reaction is carried through as a one-pot reaction.

Furthermore, particularly suitable are orthoesters the alcohol moietiesof which derive from the following glycidyl alcohols:

2,3-Epoxy-2-methyl-3-phenyl-1-propanol ═2-methyl-3-phenylglycidol##STR2## (corresponding to orthoester 9) 2,3-Epoxy-2-methyl-1-propanol##STR3## (corresponding to orthoester 10) 2,3-Epoxy-1-propanol ##STR4##(corresponding to orthoester 11)

The orthoesters 9 to 11 belong to a second group of new orthoestersaccording to the present invention, i.e. orthesters of the generalformula ##STR5## wherein: R¹ is hydrogen or an organic residue;

R³ is hydrogen or an alkyl group of 1 to 6 carbon atoms; and

R⁴ is hydrogen, an alkyl group or a phenyl group.

According to the present invention, the orthoesters of the generalformula (4) are prepared by transesterification of an orthoester of thegeneral formula

    R.sup.1 C O--R.sup.5 --CH.sub.3 !.sub.3                    ( 8),

wherein R⁵ is (CH₂)_(m), m being an integer from 0 to 5, with an alcoholof the general formula ##STR6##

Other suitable orthoesters are described in the publication of Robert H.DeWolfe, Carboxylic Ortho Acid Derivatives, Academic Press 1970 (OrganicChemistry Series Monographs No. 14).

For the treatment of the substrate with said orthoesters, the substrateis preferably pre-dried, e.g. at 150° C./1 to 3 mbar. The application ofthe orthesters is preferably effected at room temperature, thisparticularly for acrylic compounds, or under reflux, or in the gasphase.

If the alcohol moiety of the orthoester is unsaturated or epoxidized,the modified surface may be reacted further with other reactivecompounds.

In this way, either

an adhesive layer or a coating compound can be directly anchored on thesurface of the modified substrate (cf. compounds of group 1 hereafter);

or

a polymeric layer comprising active hydrogen atoms can be formed on thesurface of the modified substrate, which is thereafter further reactedwith an adhesive or a coating compound which is able to form chemicalbonds with said reactive hydrogen atoms (cf. compounds of group 2hereafter).

Examples of suitable compounds for said further reaction withunsaturated alcohol moieties are:

1 Unsaturated compounds without active hydrogen atoms, particularly:

1.1 Monomers having at least one olefinic double bond;

1.2 Alkylacrylates and/or alkylmethacrylates;

1.3 Styrene and/or acrylonitrile;

2 Unsaturated compounds having active hydrogen atoms, particularly:

2.1 Compounds of the general formula ##STR7## wherein:

R and R' independently from each other are a hydrogen atom or asubstituent having at least one active hydrogen atom; and

R" is a hydrogen atom or a substituent having at least one activehydrogen atom or a lower alkyl group or CN;

X is an oxgen or sulfur atom or the residue NH; e.g.:

2.1.1 acrylic acid;

2.1.2 2-hydroxyethylacrylate;

2.1.3 4-hydroxybutylacrylate;

2.1.4 2,3-dihydroxypropylacrylate; =glycerylmonoacrylate;

2.1.5 2,3-dihydroxypropylmethacrylate =glycerylmonomethacrylate;

2.1.6 hydroxypropylmethacrylate; or

2.1.7 acrylamide;

2.2 Compounds of the general formula ##STR8##

wherein:

n is an integer from 0 to 18; and

Y is an oxygen or sulfur atom or one of the residues NH, COO and SO₃ ;e.g.:

2.2.1 4-hydroxystyrene; or

2.2.2 4-aminostyrene;

2.3 Unsaturated dicarbonic acids and/or their anhydrides; e.g.:

2.3.1 maleic acid and/or maleic anhydride;

2.4 Epoxyacrylates and/or epoxymethacrylates; e.g.:

2.4.1 2,3-epoxypropylacrylate; or

2.4.2 2,3-epoxypropylmethacrylate.

The classes of compounds mentioned above can be combined at will, i.e.each molecule of the treated substrate can be reacted further with eachof the said classes of compounds.

Preferably, the reaction of said unsaturated compounds with anunsaturated alcohol fixed on the substrate is effected by radicalicpolymerization in the presence of azoisobutyric nitrile ordibenzoylperoxide as radical former.

Upon the further reaction of the modified surfaces with said reactivecompounds, a polymer which is firmly anchored on the surface of thesilicon dioxide substrate is obtained.

Particularly suitable for the further reaction of modified surfaceswhich are occupied by epoxidized alcohols are epoxy compounds andisocyanates.

EXAMPLE 1

Synthesis of Triallylorthoformate=Orthoformic AcidAllylester=Triallyloxymethane (Compound 7)

140.5 g (1 mole) of benzoylchloride was dropwise added within 20 minutesto a stirred and cooled mixture of 45 g (1 mole) of formamide, 174 g (3mole) of allylalcohol and 200 ml of petroleum ether. The solution wasstirred for 1 hour at 35° C., and the formed ammonium chloride and theformed benzoic acid were filtered off. The filtrate was dropwise addedto 500 ml of a cooled and stirred sodium hydroxide solution. The organicphase was separated in a separating funnel, washed with 50 ml of waterand dried overnight over CaH₂.

Yield: 123.7 g (61% of theory)

    ______________________________________                                        .sup.1 H--NMR:                                                                         s      5,30 ppm (1 H)                                                                            .sup.13 C--NMR:                                                                       111,53 ppm                                         dxt    4,12 ppm (6 H)       65,13 ppm                                         dxdxt  5,93 ppm (3 H)      134,05 ppm                                         dxdxt  5,18 ppm            116,98 ppm                                         dxdxt  5,31 ppm (3 H)                                                ______________________________________                                    

EXAMPLE 2

Synthesis of triglycidylorthoformate (Compound 11)

30 mg of p-toluenesulfonic acid monohydrate, dissolved in 1 ml ofmethanol, were added to a mixture of 3.15 g (0.297 mole) oftrimethylorthoformate (compound 1--b.p.75=44° C.) and 106.5 g (1.44 mol)of glycidol (b.p.0,006=26° C.).

The reaction mixture was heated to 110° C., so that the clear solutionsimmered. Thereby, during about 1 hour about 12 ml (0.3 mole) of formedmethanol distilled off through a Vigreux column (10 cm). During thefollowing 5 hours the pressure was slowly but continuously reduced to100 mbar by means of a water jet pump, in such a manner that thereaction mixture always simmered, but the vapor temperatur did notexceed the boiling temperature of methanol. For completing the reaction,boiling was continued for another 3 hours at 110° C. and 100 mbar (totalreaction time: 9 hours). Altogether, about 28 ml (0.7 mol) of methanolcould be separated.

After distilling off the excess of glycidol and by-products, 14.65 g(0.063 mole) of triglycidyl orthoformate in the form of clear, oilyliquid were distilled off at 0.009 mbar and a vapour temperature of 138°C..

Analysis of triglycidyl orthoformate:

Yield: 14.65 g (21% of theory), B.P.0.07: 138° C., n_(D) ²⁰ : 1.463

    ______________________________________                                        Microanalysis:                                                                           C            H       O                                             ______________________________________                                        calculated:                                                                              51.72%       6.94%   41.34%                                        fpound     51.74%       6.80%   41.48%                                        ______________________________________                                    

FT-IR (mesured as liquid film betweeen 2 salt plates)

    ______________________________________                                        3060 w, 3002 m CH st (epoxide)                                                2932 m, 2888 m CH st (CCH)                                                    1483 w, 1458 w, 1428 w                                                                       CH.sub.2 delta                                                 1256 m         COC st as (epoxide)                                            1101 s, 1063 s COC st as (HCOCH.sub.2)                                        .sup.1 H-NMR (200 MHz, CDCl.sub.3):                                           delta (Ha) delta (Hb) delta (Hc) delta (Hd) delta (He) delta                         = = = = = =                                                                          3.83 ppm 3.83 ppm 3.48 ppm 3.13 ppm 2.76 ppm 2.58                                       ##STR9##                                              .sup.13 C-NMR (50 MHz; CDCl.sub.3):                                           delta (Ca) delta (Cb) delta (Cc) delta (Cd)                                          = = = =                                                                              112 ppm  65 ppm  50 ppm  44 ppm                                                         ##STR10##                                             ______________________________________                                    

Remark:

Since the carbon atom C_(c) is a chiral center, there are 2 pairs ofenantiomers of triglycidyl orthoformate which show slightly differentchemical shifts.

EXAMPLE 3

Treatment of Substrates with Orthoesters

Glass plates, silicon, silicon dioxide and Aerosil 200 were dried at10⁻² mbar, dipped overnight into 2% solutions of ortho-ester in CCl₄,and refluxed overnight. In the case of Aerosil, the reaction productswere analyzed by means of IR- and ¹³ C-solid-NMR-spectroscopy, as wellas by means of TGA (Thermogravimetric Analysis). The portion of organicproduct on Aerosil 200 typically was about 3% by weight.

The central carbon atoms of the orthoesters had disappeared in all casesfrom the ¹³ C-NMR-spectrum; only the signals of the correspondingalcohols were visible.

For compounds of the general formula RC OR'!₃, wherein R=aryl andR'=alkyl, only C-H-vibrations of alkyl groups could be observed, whereasfor R=alkyl and R'=aryl, only signals of aromatic C-H-stretchingvibrations were present in the IR-spectrum.

EXAMPLE 4

Treatment of Aerosil 200 with Tri(2,3-epoxy-1-propyl)orthoformate=Orthoformic Acid Glycidylester=Triglycidylorthoformate

Aerosil 200 was dried at 120° C./10⁻² mbar for 1 hour, immersed into a10% solution of said orthoester in CCl4, and stirred at room temperaturefor 3 hours. The reaction product was analyzed by means of IR- and ¹³C-solid-NMR-spectroscopy, as well as by means of TGA (ThermogravimetricAnalysis). The portion of organic product on Aerosil 200 typically wasabout 3 to 5% by weight.

The central carbon atom of the orthoester had disappeared in all casesfrom the ¹³ C-NMR-spectrum; only the signals of the correspondingepoxyalcohol were visible.

EXAMPLE 5

Polymerization

130 mg of dibenzoylperoxide (recrystallized from CHCl₃ /MeOH) weredissolved in 100 ml of freshly distilled styrene and 20 ml of freshlydistilled methacrylic acid.

Glass plates, silicon, silicon dioxide and Aerosil, which had beentreated according to the directions of Example 2 withtri(ethylacryl)orthoformate, were dried at 10⁻² mbar and then reactedfor 8 hours at 60° C. with a styrene/methacrylic acid/dibenzoylperoxidesolution. The portion of organic product on Aerosil 200 was 15% byweight. This portion did not change even after washing for 3 days withtetrahydrofuran, chloroform, carbon tetrachloride, dimethylsulfoxide ortoluene. In the IR-spectrum signals of acid groups and phenyl ringscould be identified.

EXAMPLE 6

The results of the measurements of the boundary and contact angles forwater on various substrates immediately after the treatment with thestated orthoesters and/or after treatment of the treated surfaces withvarious solvents in an ultrasonic bath are compiled hereafter.

"Si(300AOx)" stands for a silicon layer having a surface layer ofsilicon dioxide of a thickness of 300 A.

The extracting agents are abbreviated as follows:

    ______________________________________                                        CCl.sub.4                                                                           Carbon tetrachloride = tetrachloromethane                               EtOH  Ethanol                                                                 THF   Tetrahydrofuran = tetramethyleneoxide                                   DMSO  Dimethylsulfoxide                                                       H.sub.2 O                                                                           Water                                                                   6.1 Trimethylorthoformate = orthoformic acid methylester =                    trimethoxymethane                                                             Extraction        Glass   Quartz                                                                              Si(300ÅOx)                                                                        Silicon                               ______________________________________                                        CCl.sub.4                                                                             15 minutes                                                                              44°                                                                            57°                                                                          62°                                                                            69°                            CCl.sub.4                                                                             15 hours  44°                                                                            55°                                                                          75°                                                                            75°                            EtOH    15 minutes                                                                              32°                                                                            36°                                                                          50°                                                                            62°                            EtOH     3 hours  38°                                                                            34°                                                                          47°                                                                            64°                            THF     15 minutes                                                                              45°                                                                            41°                                                                          51°                                                                            67°                            Untreated          8°                                                                            14°                                                                          46°                                                                            42 . . . 70°                   ______________________________________                                        6.2 Triethylorthoformate = orthoformic acid ethylester =                      triethoxymethane                                                              Extraction        Glass   Quartz                                                                              Si(300ÅOx)                                                                        Silicon                               ______________________________________                                        Unextracted       50°                                                                            47°                                                                          72°                                                                            78°                            CCl.sub.4                                                                             15 min    60°                                                                            64°                                                                          75°                                                                            82°                            CCl.sub.4                                                                             15 h      60°                                                                            50°                                                                          70°                                                                            78°                            EtOH    15 min    50°                                                                            47°                                                                          70°                                                                            78°                            EtOH    15 h      49°                                                                            46°                                                                          68°                                                                            78°                            THF     15 min    49°                                                                            46°                                                                          68°                                                                            78°                            Acetone 15 min    48°                                                                            46°                                                                          67°                                                                            78°                            DMSO    15 min    49°                                                                            45°                                                                          68°                                                                            80°                            H.sub.2 O                                                                             15 min    50°                                                                            44°                                                                          62°                                                                            78°                            Untreated          8°                                                                            14°                                                                          46°                                                                            42 . . . 70°                   ______________________________________                                        6.3 Tributylorthoformate = orthoformic acid butylester =                      tributoxymethane                                                              Extraction        Glass   Quartz                                                                              Si(300ÅOx)                                                                        Silicon                               ______________________________________                                        Unextracted       70°                                                                            53°                                                                          78°                                                                            93°                            CCl.sub.4                                                                             15 minutes                                                                              70°                                                                            58°                                                                          78°                                                                            93°                            CCl.sub.4                                                                             15 hours  59°                                                                            58°                                                                          77°                                                                            90°                            EtOH    15 minutes                                                                              49°                                                                            30°                                                                          48°                                                                            91°                            DMSO    15 minutes                                                                              48°                                                                            32°                                                                          35°                                                                            85°                            H.sub.2 O                                                                             15 minutes                                                                              42°                                                                            30°                                                                          33°                                                                            90°                            Untreated          8°                                                                            14°                                                                          46°                                                                            42 . . . 70°                   ______________________________________                                        6.4 Triallylorthoformate = orthoformic acid allylester =                      triallyloxymethane                                                            Extraction        Glass   Quartz                                                                              Si(300ÅOx)                                                                        Silicon                               ______________________________________                                        CCl.sub.4                                                                             15 min    45°                                                                            50°                                                                          66°                                                                            93°                            CCl.sub.4                                                                             15 h      46°                                                                            47°                                                                          67°                                                                            93°                            EtOH    15 min    48°                                                                            43°                                                                          66°                                                                            93°                            THF     15 min    46°                                                                            45°                                                                          64°                                                                            90°                            Acetone 15 min    46°                                                                            42°                                                                          62°                                                                            90°                            DMSO    15 min    44°                                                                            44°                                                                          63°                                                                            90°                            H.sub.2 O                                                                             15 min    39°                                                                            30°                                                                          49°                                                                            87°                            Untreated          8°                                                                            14°                                                                          46°                                                                            42 . . . 70°                   ______________________________________                                    

These examples show that the compounds applied to the surfaces by meansof orthoesters, acetals or ketals are not only very resistant toextraction but that the boundary or contact angle in some cases is evenincreased and thus the wettability is reduced. This is due to the factthat the solvents wash away adsorbed polar compounds from the surface.

EXAMPLE 7

Shear Tension Test Following DIN 54451

Adhesive: BETASEAL® HV-3 (registered Trade Mark of Gurit-Essex AG,CH-8807 Freienbach)

Adhesive area: 25×10 mm

Hight of adhesive strand: 2 mm

Bonded materials: electrophoretically primed sheet metal 100×25×1 mm;and Glass 100×25×5 mm

A=untreated

B=treated with BETASEAL® WIPE VP 04604 (registered Trade Mark ofGurit-Essex AG, CH-8807 Freienbach)

C=treated according to Example 4

Hardening: 7 days at 23° C./50% realtive humidity

    ______________________________________                                                      A       B         C                                             ______________________________________                                        Combined tension and shear                                                                    1.1       6.2       6.3                                       resistance  N/mm.sup.2 !                                                      Kind of fracture                                                                              adhesive  cohesive  cohesive                                  ______________________________________                                    

Aging: 7 days at 70° C./100% relative humidity+1 day at -20° C.

    ______________________________________                                        Combined tension and shear                                                                    0.9      3.5        5.1                                       resistance  N/mm.sup.2 !                                                      Kind of fracture                                                                              adhesive 80% cohesive                                                                             cohesive                                  ______________________________________                                    

EXAMPLE 8

Heat Resistance of the Surface Modification

The desorption temperatures of various alcohols adsorbed on Aerosil 200,the surface of which was modified according to Example 2 bytriethylorthoformate, were analyzed by means of TGA (ThermogravimetricAnalysis) under nitrogen. The results are compiled in the followingTable.

    ______________________________________                                                   Desorption temperature                                                                     Loss in weight                                                    °C.!  %!                                                   ______________________________________                                        Methanol     485            1.6                                               Ethanol      570            2.0                                               Butanol      550            1.8                                               Allylalcohol 550            2.0                                               2-Hydroxyacrylate                                                                          430            2.0                                               Phenol       195            2.8                                               ______________________________________                                    

EXAMPLE 9

Stability of Surface Modification Against Water

It was tried to substitute ethanol which was adsorbed on Aerosil 200,the surface of which had been modified according to Example 2 bytriethylorthoformate, by water. For this purpose the product wascontaced with water in various ways:

Desorption experiments:

a) 17 months stored in air at room temperature;

b) 1 month stored in an atmosphere saturated with water at roomtemperature;

c) 1 week stirred in water at room temperature;

d) 3 days boiled in water, about 100° C.;

e) 1 week extracted in a Kumagawa extractor, about 100° C.

When it was tried to bring the product into water, it turned up that theproduct no longer behaved hydrophilic as it did before treatment withthe orthoester, but had taken a hydrophobic character. This resulted ina modified wettability. When it was tried to suspend it, it floated onthe water. On the other hand, if the product was first introduced andthe water was added afterwards, an air bubble was formed around theproduct. Only by vigorous stirring it was possible to supend theproduct. After this mechanical mixing it was no longer possible todetermine whether or not the product was wetted.

No change with respect to adsorbed alcohol and water content could bedetermined by means of IR-spectroscopy in tests b) to e).

What is claimed is:
 1. A silicon substrate or silicon dioxide substratehaving at least one surface comprising alcohol or silylether moietiesprepared by contacting a surface of said substrate with at least oneorthoester.
 2. A substrate according to claim 1, wherein said alcoholand silylether moieties comprise saturated aliphatic residues.
 3. Asubstrate according to claim 1, wherein said alcohol or silylethermoieties comprise unsaturated aliphatic residues.
 4. A substrateaccording to claim 3, wherein said unsaturated alcohol or silylethermoieties have been reacted with at least one unsaturated compound.
 5. Asubstrate according to claim 4, wherein said unsaturated alcohol orsilylether moieties have been reacted with at least one unsaturatedcompound without active hydrogen atoms.
 6. A substrate according toclaim 4, wherein said unsaturated alcohol or silylether moieties havebeen reacted with at least one unsaturated compound containing activehydrogen atoms.
 7. A substrate according to claim 6, wherein saidunsaturated alcohol or silylether moieties have been reacted with atleast one compound of the general formula ##STR11## wherein: R and R'independently from each other are a hydrogen atom or a substituenthaving at least one active hydrogen atom;R" is a hydrogen atom or asubstituent having at least one active hydrogen atom or an alkyl residueor CN; and X is an oxygen or sulfur atom or the residue NH.
 8. Asubstrate according to claim 6, wherein said unsaturated alcohol orsilylether moieties have been reacted with acrylamide.
 9. A substrateaccording to claim 6, wherein said unsaturated alcohol or silylethermoieties have been reacted with at least one unsaturated compound of thegeneral formula ##STR12## wherein: n is an integer from 0 to 18; andY isan oxygen or sulfur atom or one of the residues NH, COO or SO₃.
 10. Asubstrate according to claim 9, wherein said unsaturated alcohol orsilylether moieties have been reacted with 4-hydroxystyrene or4-aminostyrene.
 11. A substrate according to claim 6, wherein saidunsaturated alcohol or silylether moiety has been reacted with at leastone unsaturated dicarbonic add or its anhydride.
 12. A substrateaccording to claim 6, wherein said unsaturated alcohol or silylethermoiety has been reacted with at least one epoxyacrylate orepoxymethacrylate.
 13. A substrate according to claim 1, wherein saidsubstrate comprises a silicate filler.
 14. A substrate according toclaim 1, wherein said substrate comprises silicate fibers.
 15. Asubstrate according to claim 1, wherein said substrate is a flat glass.16. A substrate according to claim 1, wherein said substrate is asilicon wafer.
 17. A substrate according to claim 1, wherein saidsubstrate is an aerogel glass.
 18. A method of treating a siliconsubstrate or silicon dioxide substrate to improve the adhesion oforganic compositions thereto, comprising contacting a surface of saidsubstrate with at least one orthoester.
 19. The method of claim 18,wherein said substrate surface is contacted with an orthoester having asaturated alcohol moiety.
 20. The method of claim 18, wherein saidsubstrate surface is contacted with an orthoester having an unsaturatedalcohol moiety.
 21. The method of claim 20, wherein said substratesurface is further contacted with at least one unsaturated compoundother than an orthoester.
 22. The method of claim 21, wherein saidunsaturated compound other than an orthoester is an unsaturated compoundwithout active hydrogen atoms.
 23. The method of claim 21, wherein saidunsaturated compound other than an orthoester is an unsaturated compoundhaving active hydrogen atoms.
 24. The method of claim 23 wherein saidunsaturated compound having active hydrogen atoms is a compound of thegeneral formula ##STR13## wherein: R and R' independently from eachother are a hydrogen atom or a substituent having at least one activehydrogen atom;R" is a hydrogen atom or a substituent having at least oneactive hydrogen atom or an alkyl residue or CN; and X is an oxygen orsulfur atom or the residue NH.
 25. The method of claim 23, wherein saidunsaturated compound having active hydrogen atoms is acrylamide.
 26. Themethod of claim 23, wherein said unsaturated compound having activehydrogen atoms is a compound of the general formula ##STR14## wherein: nis an integer from 0 to 18; andY is an oxygen or sulfur atom or one ofthe residues NH, COO or SO₃.
 27. The method of claim 26, wherein saidunsaturated compound having active hydrogen atoms is 4-hydroxystyrene or4-aminostyrene.
 28. The method of claim 23, wherein said unsaturatedcompound having active hydrogen atoms is a dicarbonic acid or itsanhydride.
 29. The method of claim 23, wherein said unsaturated compoundhaving active hydrogen atoms is an epoxyacrylate or epoxymethacrylate.30. A substrate according to claim 2 wherein said saturated aliphaticresidues are residues of methanol, ethanol, propanol or butanol.
 31. Asubstrate according to claim 1 wherein said alcohol or silylethermoieties comprise glycidyl alcohol moieties or glycidyl silylethermoieties.
 32. A substrate according to claim 3 wherein said unsaturatedaliphatic residues are residues of allyl alcohol or 2-hydroxyethylacrylate.
 33. A substrate according to claim 5 wherein said unsaturatedcompound without active hydrogen atoms is selected from the groupconsisting of compounds having at least one olefinic double bond,alkylacrylates, alkylmethacrylates, styrene and acrylonitrile.
 34. Asubstrate according to claim 7 wherein said unsaturated alcohol orsilylether moieties have been reacted with at least one unsaturatedcompound selected from the group consisting of acrylic acid,2-hydroxyethylacrylate, 4-hydroxybutylacrylate,2,3-dihydroxypropylacrylate, 2,3-dihydroxypropylmethacrylate, andhydroxypropylmethacrylate.
 35. A substrate according to claim 11,wherein said unsaturated alcohol or silylether moiety has been reactedwith maleic acid or maleic anhydride.
 36. A substrate according to claim12, wherein said unsaturated alcohol or silylether moiety has beenreacted with 2,3-epoxypropylacrylate or 2,3-epoxypropylmethacrylate. 37.A substrate according to claim 13, wherein said substrate is selectedfrom the group consisting of pyrogenic silicic acid, precipitatedsilicic acid, silica gel, quartz powder and glass powder.
 38. Asubstrate according to claim 14, wherein said substrate is selected fromthe group consisting of glass fibers, glass textiles, glass wool, androck wool.
 39. A substrate according to claim 15, wherein said substrateis selected from the group consisting of a window glass composite,insulating glass system, optical glass, and glass membrane.
 40. Asubstrate according to claim 16, wherein said silicon wafer is anoxidized wafer.
 41. The method of claim 19, wherein said saturatedalcohol moiety comprises a saturated aliphatic residue.
 42. The methodof claim 41, wherein said saturated aliphatic residue is derived frommethanol, ethanol, propanol or butanol.
 43. The method of claim 18,wherein said substrate surface is contacted with an orthoester having analcohol moiety derived from a glycidyl alcohol.
 44. The method of claim20, wherein said unsaturated alcohol moiety comprises an unsaturatedaliphatic residue.
 45. The method of claim 44, wherein said unsaturatedaliphatic residue is derived from allyl alcohol or2-hydroxyethylacrylate.
 46. The method of claim 21, wherein saidunsaturated compound other than an orthoester is selected from the groupconsisting of alkylacrylates, alkylmethacrylates, styrene andacrylonitrile.
 47. The method of claim 24, wherein said unsaturatedcompound having active hydrogen atoms is selected from the groupconsisting of acrylic acid, 2-hydroxyethylacrylate,4-hydroxybutylacrylate, 2,3-dihydroxypropyl-acrylate,2,3-dihydroxypropylmethylacrylate and hydroxypropylmethacrylate.
 48. Themethod of claim 28, wherein said unsaturated compound having activehydrogen atoms is maleic acid or maleic anhydride.
 49. The method ofclaim 29, wherein said unsaturated compound having active hydrogen atomsis 2,3-epoxypropylacrylate or 2,3-epoxypropylmethacrylate.
 50. A methodfor improving the adhesion of an organic composition to the surface of asilicon or silicon dioxide substrate, comprising:(1) first, contactingsaid surface of said substrate with an orthoester; and (2) second,contacting said substrate surface with said organic composition orprecursor thereof.
 51. The method of claim 50, wherein said orthoesteris selected from compounds of the general formula R¹ --C OR² !₃,wherein:R¹ is hydrogen or an alkyl group having 1 to 4 carbon atoms andR² is an alkyl group having 1 to 4 carbon atoms or an allyl group. 52.The method of claim 50, wherein said orthoester is selected fromcompounds of the formula R¹ C OR² --O--CO--CH═CH₂ !₃, wherein:R¹ ishydrogen or an organic residue; and R² is (CH₂)_(n) where n is aninteger from 1-18.
 53. The method of claim 50, wherein said orthoesteris selected from compounds of the general formula ##STR15## wherein: R¹is hydrogen or an organic residue;R³ is hydrogen or an alkyl group of 1to 6 carbon atoms, and R⁴ is hydrogen, an alkyl group or a phenyl group.54. The method of claim 52, wherein said organic composition precursoris selected from the group consisting of monomers having at least oneolefinic double bond, alkylacrylates, alkylmethacrylates, styrene,acrylonitrile, compounds of the general formula ##STR16## wherein R andR' independently from each other are a hydrogen atom or a substituenthaving at least one active hydrogen atom;R" is a hydrogen atom, asubstituent having at least one active hydrogen atom, an alkyl residue,or CN; and X is an oxygen or sulfur atom, or the residue NH,compounds ofthe general formula ##STR17## wherein: n is an integer from 0 to 18; andY is an oxygen or sulfur atom or one of the residues NH, COO or SO₃;unsaturated dicarbonic acids, unsaturated dicarbonic acid anhydrides,epoxyacrylates and epoxymethacrylates.
 55. The method of claim 54,wherein said organic composition precursor is selected from the groupconsisting of acrylic acid, 2-hydroxyethylacrylate,4-hydroxybutylacrylate, 2,3-dihydroxypropylacrylate,2,3-dihydroxypropylmethacrylate, hydroxypropylmethacrylate, acrylamide,4-hydroxystyrene, 4-aminostyrene, maleic acid, maleic anhydride2,3-epoxypropylacrylate, and 2,3-epoxypropylmethacrylate.
 56. The methodof claim 55, wherein said orthoester is tri(ethylacrylate)orthoformate.57. A silicon substrate or silicon dioxide substrate prepared by themethod of claim
 43. 58. A silicon substrate or silicon dioxide substrateprepared by the method of claim
 56. 59. A silicon substrate or silicondioxide substrate prepared by the method of claim
 53. 60. A siliconsubstrate or silicon dioxide substrate prepared by the method of claim54.
 61. A silicon substrate or silicon dioxide substrate prepared by themethod of claim
 55. 62. Ortoesters of the general formula ##STR18##wherein: R¹ is hydrogen or an organic residue; andR³ is hydrogen or amethyl group.